Along railway trucks, detection boxes emit beams of infrared light directed to the extremities of the axles of the bogies, more or less in the region of the rolling bearing of the axle box, in order to detect abnormal temperatures of this region, caused by friction in damaged bearings.
The rolling bearings of a bogie may be maintained on the axle by an end cap screwed to the axle. They are then, in addition protected by a closed lid covering both the end cap, and the seal region of the bearing. In such a closed axle box, the end cap is secured by screws to the axle and contacts the inner bearing ring, whereas the external lid is assembled to a core part of the axle box and contacts the outer bearing ring. In this way, the temperature of the lid is a consequence of the temperature of the outer bearing ring.
In other embodiments, simplified open axle boxes have been developed, in which the end cap and lid are replaced by an extended end cap covering the inner ring of the rolling bearing and also covering part of the seal of the rolling bearing. Bogies with such simplified axle boxes are prone to erroneous failure detection by the infrared hotbox detectors.
Critical temperatures may be wrongly detected on such a simplified axle box, even if the rolling bearing is in good working order. As a matter of fact, high temperatures of external seals of the axle box may be measured or high temperatures of screw bolts holding the end cap. Both temperatures are usually higher than the temperature of the rings of the roller bearing, which are actually the temperatures to be surveyed.
The present invention aims at proposing an end cap for a simplified axle box, which can be used without an external lid, and which can be subjected to infrared temperature detection with at least the same accuracy detection, as when the infrared beams are directed towards the lid of a closed axle box.